St Mary’s church is a small, two-celled structure with an early chancel arch, baptismal font and added S arcade with two arches. Post medieval additions to the church include S and E chancel windows, which appear to date from the 16thc and a bellcote of 1724. The chancel seems also to have been extended at an uncertain date. The church was restored in 1878 and a new vestry added in 1888.

Gilcrux is located within the medieval region of Allerdale, whose lord in the late 11thc was Waltheof/Waldeve, son of Gospatric. Waltheof managed to hold his lands after the Normans invaded and appears to have been enfeoffed by Ranulph Meschin, who held all of Cumbria through the crown. After Randolph Meschin became Earl of Chester following the White Ship disaster of 1120, his brother William seems to have sub-granted a thin section of land in Copeland to Waltheof, which was to become the honour of Cockermouth. Waldeve gave Gilcrux to Adam, son of Liulf (or Lyulph). It later passed to the family of Bonekill through marriage. Land at Gilcrux was given to the abbey of Calder in the middle or second half of the 13thc by Thomas and Walter Bonekill. In 1357 the abbot of Calder Abbey, before the bishop of Carlisle, proved the abbey’s title to the church at Gilcrux. Following the dissolution of the monasteries, the rectory of Gilcrux was leased to William Leigh and the manor to Alexander Armstrong. The manor, however, soon reverted to the crown and eventually to John Soukey and Persival Gunson by grant of Elizabeth I. Subsequently, it came into the hands of the Dykes family. In the taxatio of about 1291/2 the church of ‘Gilecruce’ , listed within the grouping for the Deaconry of Allerdale, was valued at £2.6s.8d.

The Domesday Book did not cover this part of England. In fact, there are few documents surviving concerning the church at Gilcrux and none known to exist before the 13thc. Preserved inside the church is an Anglo-Saxon cross head, which confirms that there was a religious site at Gilcrux prior to the arrival of the Normans in 1092. The late 13thc taxation roll testifies to the fact that the parish was not a rich one. Cox states that the baptismal font and cross-head are the oldest details in the church. He also states that Bishop Nicolson in 1703 said that the font was ‘broken and Lumpish’. The chancel arch looks early, as does the font and may suggest a date in the early 12thc, a date proposed by others. The S nave arcade must have been built later, probably still in the 12thc, though it remains rather simple compared with arcades found elsewhere. A date in the early 13thc cannot, however, be discounted. The carved head may possibly date to the same period, but this is not certain.